Hindered tris (meta-hydroxybenzyl)cyanurate antioxidants

ABSTRACT

Compounds of the formula:   WHEREIN R is a branched chain alkyl group containing three to about twelve carbon atoms are provided. These compounds are useful as antioxidants in organic substrates, such as polyolefins, rubber, etc. They can be prepared by reacting three moles of 4-alkyl-3-hydroxy-2,6-dimethylbenzyl chloride with one mole of cyanuric acid.

Unite States atent [191 Susi [ Jan. 21, 1975 [75] Inventor: PeterVincent Susi, Middlesex, NJ.

[73] Assignee: American Cyanamid Company,

Stamford, Conn.

22 Filed: on. 20, 1972 21 Appl. No.: 299,565

Related US. Application Data [62] Division of Ser. No. 199,340, Nov. 16,1971, Pat. No.

[52] US. Cl 252/403, 252/515 R, 252/405, 260/45.8 N, 260/248 NS,426/228, 426/328, 426/182 [51] Int. Cl. C07d 55/38, BOlj 1/16, C1 1b5/00 [58] Field of Search 252/403, 51.5 R, 405; 260/248 NS, 45.8;426/328, 228, 182

[56] References Cited UNITED STATES PATENTS 3,531,483 9/1970 Gilles260/248 NS 3,723,428 3/1973 Song 260/248 CS Primary Examiner-Benjamin R.Padgett Assistant Examiner-Irwin Gluck Attorney, Agent, or FirmPhilipMintz [57] ABSTRACT Compounds of the formula:

II A -cH,/v N' R I) a 7 0 C II cl! cu,

wherein R is a branched chain alkyl group containing three to abouttwelve carbon atoms are provided. These compounds are useful asantioxidants in organic substrates, such as polyolefins, rubber, etc.They can be prepared by reacting three moles of 4 alkyl-3-hydroxy-2,6-dirnethylbenzyl chloride with one mole of cyanuric acid.

5 Claims, No Drawings HINDERED TRIS (META-HYDROXYBENZYL)CYANURATEANTIOXIDANTS This is a division of application Ser. No. 199,340, filedNov. 16, 1971, now U.S. Pat. No. 3,723,427.

This invention relates to novel compounds useful for inhibitingoxidative degradation of organic materials. More particularly, itrelates to compounds of the formula:

wherein R is a branched chain alkyl group containing three to abouttwelve carbon atoms. This invention also relates to the use of suchcompounds to inhibit oxidative degradation of organic materials subjectthereto.

It is well known that numerous organic materials tend to deteriorateupon exposure to oxygen in air. Among such materials are polyolefins,ABS resins, polyamides, polyacetals, polystyrene, impact polystyrene,natural and synthetic rubbers including ethylene-propylene copolymersand carboxylated latices, fats, oils, greases, gasoline, etc. It is alsowell known to incorporate various additives (antioxidants) into suchmaterials to inhibit oxidative degradation thereof. This inventionarises out of the continuing search for new compounds which will besuperior antioxidants for such materials.

The present invention is based on the discovery that these novelcompounds, as defined in the above formula, in addition to inhibitingoxidation of organic materials, such as those mentioned above, possessoutstanding resistance to extraction by boiling water, a property whichhas considerable importance when used in plastic materials inapplications such as fibers, washing machine agitators, dish washerparts, and the like, where contact with hot water is likely. Inaddition, these compounds are useful processing antioxidants forpolyolefins; that is, they protect the polymer against breakdown duringmilling, extrusion, and other hightemperature processing operations.

In the compounds of the present invention, the three nitrogens of thecyanuric acid are each connected to a hindered phenolic moiety through amethylene group. It will be noted that the hydroxyl group of eachphenolic moiety is positioned meta with respect to the methylene groupattaching the phenolic moiety to the cyanuric acid. It is criticallyimportant that this hydroxyl group be located in the meta position toavoid discoloration of the substrate in which these compounds are usedand to provide a high degree of antioxidant protection to the substrate.It will also be noted that all positions ortho and para to the hydroxylgroup are substituted, one ortho position with a branched chain alkylgroup and the other two such positions with methyl groups. Thus, thisphenolic moiety is hindered by the branched chain alkyl substituentadjacent to the hydroxyl group.

Illustrative of the branched chain alkyl groups represented by R in theposition ortho to the phenolic hydroxy group in the compounds of thisinvention are isopropyl, t-butyl, sec-butyl, t-amyl, sec-heptyl,sec-octyl, t-octyl, t-nonyl (1,1-dimethylheptyl), aa'dimethylbem zyl,methylcyclopentyl, methyl cyclohexyl, and the like.

These compounds are readily prepared by known procedures, such as thereaction of one mole ofcyanuric acid with three moles of an appropriate4-alkyl-3- hydroxy-Z,6-dimethylbenzyl chloride. The benxyl chlorideutilized can be prepared from the corresponding2,4-dimethyl-6-alkylphenol by introducing the chloromethyl group intothe 3-position by reaction with by drochloric acid and formaldehyde orby reaction with methylal in the presence of hydrochloric acid andsulfuric acid according to the procedure of R. Wegler and E. Regel,Makromol, Chem. 9, 1 (1952).

These compounds (1) are non-discoloring, (2) exhibit a high degree ofantioxidant protection to the sub strate, (3) are resistant to hot waterextraction from the substrate, and (4) afford a high degree of stabilityto the substrate during mechanical processing, and are especially usefulfor inhibiting oxidative degradation of organic materials normallysubject to deterioration upon exposure to oxygen, such as thosementioned above. These compounds may be incorporated into the variousorganic materials to be protected by any of the standard techniques,including stirring, milling, screw extruding, Banbury mixing, swelling,etc. These compounds are effective over a wide concentration range ofabout 0.01 to about 5.0 percent based on weight of material to beprotected. ln polypropylene, a preferred use, they are preferably usedat a concentration between 0.05 and 1.0 percent based on weight ofpolyolefin. After incorporating these compounds into polymericmaterials, during which other ingredients such as fillers, plasticizers,pigments, light absorbers, etc. may be added, the polymer composition isformed into use ful shapes by molding, casting, spinning, extrudinginjection molding, or other shaping procedures. In polypropylene, theantioxidant activity of these compounds can be greatly enhanced byconcurrent use therein of esters of thiodipropionic acid, such asdilauryl and dis tearyl thiodipropionate.

Oxidative deterioration of polypropylene and other similar oxidizableplastic materials is evident from the embrittlement which occurs onexposure to atmospheric oxygen. The extent to which the antioxidantprotects against deterioration is measured in an accelerated test bydetermining the hours to embrittlement at 150C. when a specimencontaining the antioxidant is exposed in a forced draft oven at thistempera ture.

Extractability of the antioxidant from the plastic by hot water isdetermined by refluxing compression molded films containing theantioxidant in water for a predetermined period of time and then agingthe specimens in a forced-draft oven as described above.

The effectiveness of these compounds as processing antioxidants isdetermined by measuring the melt-index of the polymer containing thecompound after repeated extrusions. The melt index is a measure of themelt viscosity which in turn is related to the molecular weight. Anincrease in the melt index on extrusion indicates a decrease inviscosity and a decrease in molecular weight (processing breakdown). Apolymer blend of unstabilized polypropylene containing 0.1% of thecompound and 0.25% distearylthiodipropionate (STDP) is extruded at 460F.through a 3/4% extruder and pelletized. The pellets are reextruded for atotal of four passes. The melt index of the pelletized polymer sample ismeasured after each pass, according to ASTM method D-1238. (STDP isnormally incorporated into polypropylene to improve the long-term agingproperties of phenolic antioxidants in general. The contribution of STDPto processing stability is minimal.)

The invention is more fully described in the following illustrativeexamples.

EXAMPLE 1 1,3,5-Tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-striazine-2,4,6( 1H, 3H,5H)-trione To a stirred mixture of 3.23 grams (0.025 mole) of cyanuricacid and 16.9 grams (0.075 mole) of4-tbuty1-3-hydroxy-2,6-dimethylbenzyl chloride in 50 ml.dimethylformamide at 40C. was added dropwise 12 m]. (0.08 mole) oftriethylamine. The reaction mixture was stirred for 18 hours; 50 ml.water and 50 ml. benzene were added and the two liquid layers separated.The benzene phase was washed twice with 50 ml. portions of water, theremaining water azeotropically removed, and the benzene solutionclarified with 50 g.

EXAMPLE 2 Evaluation in Polypropylene The films were aged in aforced-draft oven at 140C. and the time (hours) to embrittlementrecorded (Table 1).

Compression molded films containing the antioxidants were refluxed in200 ml. water for 7 hours 1 cy-- cle). The water was replaced at the endof each cycle until 15 cycles (105 hours) of boiling water extractionswere completed. The films were then aged as above at 150C. in aforced-draft oven and hours to embrittlement noted (Table l). Theoven-aged stability of the films after boiling water treatment is ameasure of the Superfiltrol. The benzene was removed and replacedextractability of the antioxidants.

Table 1 Additive (used at 0.2% Con- Compound Made Control No.centration) in Example 1 Comp. Add.

Oven-aging at 140C 970-980 360-370 4 Hours to Embrittlement Oven-agingat 150C after 15 cycles boiling water} 215-255 23-39 Hours toembrittlement This data shows that the compound of this invention ismuch superior in antioxidant activity as compared to the controlcompound. Of particular significance is the startling resistance toextraction by hot water, a most important property with respect tomaterials which are laundered or used immersed in water.

EXAMPLE 3 Processing Properties of Antioxidants in Polypropylene Samplesof unstabilized polypropylene containing 0.1% of the compound of Example1 and 0.25% STDP were compared with samples containing 0.1% of thecontrol compound of Example 2 and 0.25% STDP with respect to melt indexas described herein above. The data are shown in Table 11.

Table II Melt Index (ASTM-Dl238) No. of Extrusions Compound of Ex. IControl Compound The data show that the melt index of polypropylenecontaining the compound of this invention increased only 3 units after 4passes through the extruder whereas the control compound showed anincrease of 7.4 units. This indicates that the compound of thisinvention is superior to the control compound in protectingpolypropylene against polymer breakdown during processmg.

I claim:

1. A composition comprising an organic material which tends todeteriorate upon exposure to oxygen containing, in an amount effectiveto inhibit oxidative degradation thereof, a compound of the formula:

wherein R is a branched chain alkyl containing three to about twelvecarbon atoms.

2. A composition as defined in claim 1 wherein R is tertiary butyl.

3. A composition as defined in claim 1 wherein said organic material isa polyolefin.

4. A composition as defined in claim 1 wherein said organic material ispolypropylene.

5. A composition as defined in claim 4 which also contains an ester ofthiodipropionic acid.

2. A composition as defined in claim 1 wherein R is tertiary butyl.
 3. Acomposition as defined in claim 1 wherein said organic material is apolyolefin.
 4. A composition as defined in claim 1 wherein said organicmaterial is polypropylene.
 5. A composition as defined in claim 4 whichalso contains an ester of thiodipropionic acid.